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Bonding Flashcards

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1
Q

Ions

A

-Atoms are neutral, having equal number of electrons and protons.
-When atoms lose or gain electrons, they become ions.
-Cations are positive ions as they lose electrons, whereas anions are negative ions as they gain electrons.
-The periodic table can be used to find the ionic charge of an element.

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2
Q

ionic bonding

A

Ionic bonds occur between metals and non-metals.
-They form as a result of the electrostatic attraction between oppositely charged ions.
-Metals have a positive charge, whereas non-metals have a negative charge.
-The opposite charges create an electrostatic attraction between the ions, causing them to form a neutral lattice.

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3
Q

formation of an ionic compound

A

-When metals react with non-metals, electrons are transferred from the metal to the non-metal forming an ion.
-Ionic compounds are balanced, as the negative and positive charges balance each other out.
-Electron shell diagrams can be used to represent the formation of an ionic compound.

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4
Q

Physical properties of Ionic compounds

A

-The electrostatic force of attraction between oppositely charged ions arranges in a 3D structure called a lattice.
-Ionic compounds are usually solids with lattice structures.
-Ionic compounds have high melting temperatures and low volatility.
-When ionic compounds melt, they can conduct electricity.

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5
Q

Volatility

A

-Volatility is the tendency of a substance to vaporize.
-Ionic compounds have ionic bonds, which are very strong and require a lot of energy to break.
-At room temperature, there isn’t enough energy to break the lattice, making them non-volatile.

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6
Q

High melting temperatures

A

-Ionic bonds are very strong, requiring a lot of energy to break.
-Hence, ionic compounds have high melting temperatures, making them solid at room temperature.

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7
Q

Electric Conductivity

A

When ionic compounds are solid, the ions are not free to move, so they cannot conduct electricity.
-When melted, the ions are free to move, so melted ionic compounds can conduct electricity.

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8
Q

Solubility

A

Ionic compounds are soluble in polar solvents like water.
-Water can break molecules off the lattice structure, allowing the ions to be separated by polar water molecules.
-However, not all ionic compounds are soluble.

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9
Q

what is a covalent bond

A

A covalent bond is formed by the electrostatic attraction between a shared pair of electrons and the positively charged nuclei.

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10
Q

What types of elements typically form covalent bonds?

A

Covalent bonds generally occur between non-metals only.

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11
Q

What happens when atoms have similar electronegativities?

A

If atoms have similar electronegativities (the same affinity for electrons), they are likely to form a covalent bond.

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12
Q

Why do atoms with similar electronegativities share electrons?

A

Both atoms have the same affinity for electrons and neither has a tendency to donate them, therefore they must share electrons in order to achieve octet configuration and become more stable.

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13
Q

What is a double covalent bond?

A

A double covalent bond is formed when two atoms share 2 electron pairs (4 electrons).

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14
Q

What is a triple covalent bond?

A

A triple covalent bond is formed when two atoms share 3 electron pairs (6 electrons).

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15
Q

What is bond length?

A

Bond length is a measure of the distance between two bonded nuclei

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16
Q

What is bond strength?

A

Bond strength is a measure of the energy required to break the bond, described in terms of bond enthalpy.

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17
Q

How does bond length change with the number of electron pairs?

A

Bond length decreases as the number of electron pair increases because there will be a greater attractive force between the two nuclei.

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18
Q

How does bond strength change with the number of electron pairs?

A

Bond strength increases as the number of electron pair increases as more energy is required to break them.

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19
Q

What happens when electronegativities are not equal in a covalent bond?

A

When electronegativities are not equal, electrons are not shared equally and a partial ionic charge develops.

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20
Q

How can you determine the ionic character of a bond?

A

To find the most ionic bond compare the electronegative differences of each bond against the Pauling Scale. The greater the electronegative difference, the more ionic the bond is.

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21
Q

What are polar covalent bonds

A

Bonds that are partially ionic are called polar covalent bonds, and the most polar bonds will have the highest electronegative value.

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22
Q

What are non-polar covalent bonds?

A

Non-polar covalent bonds have equal sharing of bond electrons.

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23
Q

covalent compounds

A

A covalent compound is formed when non-metal atoms bond by sharing valence electrons.
Non-metals are elements that lack metallic characteristics.
The number of covalent bonds formed depends on the number of electrons needed to fill the valence shell.

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24
Q

Polar molecules

A

A polar molecule must have dipoles distributed so overall there is a positive and negative end of the molecule.
Two conditions must apply if a molecule is to be a dipole (polar): it must have polar bonds and the partial charges must be distributed asymmetrically across the molecule.
A molecule that contains polar covalent bonds will form a dipole.

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25
Q

What are covalent compounds

A

Covalent compounds are compounds that consist of two or more non-metal atoms, sharing electrons to form strong covalent bonds.

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26
Q

What are the two types of covalent structures

A

The two types of covalent structures are simple covalent and giant covalent (network covalent) structures.

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27
Q

What are simple covalent structures

A

Simple covalent structures contain only a few atoms held together by strong covalent bonds. Examples include carbon dioxide where one carbon atom is covalently bonded with two atoms of oxygen.

28
Q

Why are simple covalent structures usually liquids and gases

A

Molecular covalent substances have low boiling points and are usually liquids and gases, due to the weak intermolecular forces (not intramolecular).

29
Q

Are simple covalents conductive

A

No, simple covalent structures are non-conductive. This is because they do not have any free electrons or an overall electric charge.

30
Q

What are giant covalent structures

A

Giant covalent structures contain a lot of non-metal atoms, each joined to adjacent atoms by covalent bonds. Examples include silicon and carbon.

31
Q

Why are giant covalent structures very strong

A

The atoms in giant covalent structures are usually arranged into giant regular lattices, which are extremely strong structures because of the many bonds involved.

32
Q

Do giant covalent structures have high or low melting points?

A

Giant covalent structures have very high melting points because a lot of strong covalent bonds must be broken.

33
Q

Do all giant covalent structures have the same conductivity?

A

No, giant covalent structures vary in conductivity, as some contain free electrons while some do not.

34
Q

What are allotropes of carbon?.

A

Allotropes of carbon are three forms of carbon that contain carbon only but vary in their structure.

35
Q

What is Graphite

A

Graphite has a hexagonal layer structure, and although it has covalent bonds between the carbon atoms, it has weak Van Der Waals forces between the layers themselves, allowing the bonds to be shattered easily and the layers to slide over each other easily.

36
Q

What is the structure of graphite described as

A

the structure of graphite is described as a covalent layer lattice

37
Q

Why does graphite have good conductivity

A

Graphite has good conductivity as there are delocalized electrons between the hexagonal layers and electrons are free to move parallel.

38
Q

What is Diamond

A

In diamond, each carbon atom is joined to four other carbon atoms, forming a giant covalent structure.

39
Q

Is diamond a hard substance

A

Yes, diamond is very hard and has a high melting point because there are no weak links to the lattices.

40
Q

does diamond have good conductivity

A

No, diamond has bad conductivity as there are no delocalized electrons as the outer shell electrons are used for covalent bonds.

41
Q

What are C60 Fullerenes

A

C60 Fullerenes are spherical molecules in which 60 carbon atoms are covalently bonded to three others each.

42
Q

What is the structure of C60 Fullerenes

A

The structure of C60 Fullerenes is described as spheres made of atoms arranged in hexagons (not a lattice).

43
Q

What is silicon

A

Silicon is a member of group four of the periodic table and is able to form four covalent bonds with other silicon atoms to form network covalent structures.

44
Q

Intermolecular forces

A

Intermolecular forces exist between molecules and are weaker than intramolecular forces, which exist between atoms (ionic and covalent bonds).

45
Q

London Dispersion Forces

A
  • London dispersion force is the weakest intermolecular force.
  • This is a temporary attractive force between adjacent atoms when electrons in the atoms form temporary dipoles.
  • These forces cause non-polar substances to condense into liquids or freeze into solids.
46
Q

Dipole-Dipole

A
  • Dipole-dipole forces occur between polar molecules with both positive and negative regions.
  • These forces are dependent on the distance and orientation of the dipoles.
  • Dipole-dipole forces work only when the molecules are close to each other.
47
Q

Hydrogen Bonds

A
  • A hydrogen bond is a type of dipole-dipole force between a slightly positive hydrogen on one molecule and a slightly negative atom on another molecule.
  • Hydrogen bonds are stronger than dipole-dipole and London dispersion forces.
  • The relative strength of intermolecular bonding is: London Dispersion Forces < dipole-dipole forces < hydrogen bonds.
  • Hydrogen bonds occur when the most electronegative elements such as fluorine, oxygen and nitrogen, interact with hydrogen.
48
Q

Metallic bonding

A

Electrostatic attraction between a lattice of positive ions and delocalized electrons
Conduct electricity because they have mobile delocalized electrons
Metals are malleable and ductile because layers of metals can slide over each other when bent, hammered or stretched without breaking the metallic bond
Characteristics: Good conductors of heat and electricity, shiny, highest conductivity when they are aqueous or melted and lowest conductivity when they are gases
Alloys: result when different metals are melted together and allowed to cool, and often have enhanced properties
Alloys usually contain more than one metal and can significantly alter the properties of a metal by adding small amounts of another substance, usually another metal

49
Q

Alloys

A

Result when different metals are melted together and allowed to cool
Alloys usually contain more than one metal and have enhanced properties
Properties of a metal can be significantly altered by adding small amounts of another substance, usually another metal
Production of alloys is possible because of the non-directional nature of the delocalized electrons and the fact that the lattice can accommodate ions of different sizes
Alloys are usually stronger than regular metals because if different atoms are present, the regular network of positive ions will be disturbed
The atoms of a different size make it harder for layers of positive ions to slide over each other and thus prevent bending or denting of the metal.

50
Q

Type of Bond Comparison

A

Ionic Bonding: Very high melting point, low volatility, conduct electricity when in liquid state, some will dissolve in a polar solvent
Metallic Bonding: Medium to high melting point, usually low volatility, conduct electricity in solid state, some metals react with water to make alkaline solutions
Simple Covalent Bonding: Low melting point, high volatility, polar molecules form ions when they dissolve, dissolve in polar substances, non-polar molecules dissolve in non-polar substances
Giant Covalent Bonding: Very high melting point, low volatility, do not dissolve in any solvents, delocalized electrons in graphite, others do not have free particles or electrons

51
Q

How are covalent bonds formed

A

from the overlap of atomic orbitals

52
Q

What happens when two orbitals from different atoms merge?

A

Two orbitals from different atoms, each containing one unpaired electron, can merge in the region of space between the two atoms.

53
Q

What is the result of overlapping two orbitals?

A

This overlapping of two orbitals creates a bonding orbital between the two atoms.

54
Q

How are π-bonds formed?

A

π-bonds are formed by the sideway overlap of orbitals resulting in electron density above and below the plane of the nuclei of the bonding atom.

55
Q

How are sigma bonds formed?

A

A sigma bond is formed by the direct head-on/end-to-end overlap of orbitals resulting in electron density concentrated between the nuclei of the bonding atoms.

56
Q

what do double bonds consist of

A

one sigma bond and one pi bond

57
Q

what do triple bonds consist of

A

one sigma and two pi bonds

58
Q

What is a resonance structure?

A

Resonance structures do not change the relative positions of the atoms, but instead the electron locations.

59
Q

How are electrons located in molecules?

A

Electrons have no fixed position in molecules but can be found in certain spaces (orbitals).

60
Q

What is delocalization?

A

Delocalization involves electrons that are shared by/between more than one pair in a molecule or ion as opposed to being localized between a pair of atoms.

61
Q

What is the effect of delocalization on double bonds?

A

The electrons from the double bond have delocalized and spread themselves equally between both possible bonding positions.

62
Q

What is formal charge?

What is the most stable structure?
The most stable structure is the molecule that has a formal charge value closest to 0, with the negative charges located on the most electronegative atom.

A

Formal charge allows us to calculate which of these structures is the most stable.

63
Q

How is formal charge calculated?

A

Formal charge is calculated using the formula: FC=V-(1/2 B+L), where V=Valence electrons, B=# of bonding electrons, and L=# of lone pair electrons.

64
Q

What is the most stable structure?

A

The most stable structure is the molecule that has a formal charge value closest to 0, with the negative charges located on the most electronegative atom.

65
Q

Hybridization

A

Hybridization results from the mixing of different types of atomic orbitals on the same atom

It is written as a mix of the two combined levels

To find hybridization, we can look at the Lewis structure

If there are 4 electron domains around the central atom, the hybridization will be sp3

If there are 3 electron domains, the hybridization will be sp2

If there are 2 electron domains, the hybridization will be sp

Chemistry (4 decks)

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